These problems have already been described and discussed in detail in many patent specifications, of which a few examples are the U.S. Pat. Nos. 4,285,206 4,441,330 and 4,476,688.
Common to the majority of the known proposals for recovery techniques is that the refrigerants are handled and processed in their liquid phase. Admittedly it is relatively easy to effect a coarse cleaning of a refrigerant in the liquid phase thereof, by filtration and separation, but it is difficult and very expensive for such a technique to satisfy the increasing requirements as to the high degree of purification of the collected amounts of refrigerant.
In connection with the present invention it has been found that it is much better to concentrate on the handling and processing of the refrigerants in their gaseous phase, whereby a very high degree of purification is achievable in a more economical manner. The principle of concentrating or working on the gaseous refrigerant, however, is known already from the U.S. Pat. No. 3,699,781, and it is the purpose of the present invention to provide important improvements in the technique disclosed therein and as known otherwise.
The refrigerant in the system to be emptied is withdrawn therefrom by connecting a suction conduit from the recovering unit to a connector stub of the said system, whereby the polluted refrigerant is sucked into or through a container constituting a coarse separator for liquid and gaseous components, respectively. Already hereby a high percentage of impurities, mainly oil, will be separated for later discharge from the separator, but even a small amount of refrigerant in its liquid phase may be transferred to the separator container, more or less in admixture with the sludge of impurities. It should be prevented that such a remnant of refrigerant can leave the container by the emptying thereof, as the emptied product will normally be led into connection with the atmosphere and the atmospheric pressure, whereby the contents of refrigerant would surely escape to the atmopshere.
Particularly when it is desired to process the refrigerant in its gaseous phase it is also natural to seek to counteract the formation or collection of liquid refrigerant in the separator container by adding heat to the surroundings or otherwise arrange for a heating which will promote a boiling of the liquid refrigerant to thereby convert all of it into its gaseous phase. According to the said U.S. Pat. No. 3,699,781 this is accomplished by arranging for a heating of a portion of the conduit between the suction stub and the separator container, whereby remnants of liquid refrigerant already by its inflow to the separator will be heated for accelerated boiling such that all of it will be converted into the gaseous phase and thus not be present in the product to be let out from the bottom of the separator container.
This measure, however, has a serious drawback in that the said heating will be associated with a raised vapor pressure that will directly counteract the attainment of the desired high degree of emptying of the refrigeration system, as the increased vapor pressure will form a barrier to an almost complete emptying of the system.